This invention relates to pressurized dispensers in general and more particularly to a dispenser construction which permits increased speed in pressure filling.
Generally, pressurized containers comprise a can or bottle containing the material to be dispensed along with a pressurizing fluid, either an aerosol valve, or a pump, and a mounting cup by means of which the valve or pump is mounted on top of the can or bottle. Generally, in a valve type arrangement, there is pressure filling with a liquid propellent, whereas in a pump type arrangement, nitrogen or compressed gas is used. Typically, in a valve type arrangement an aerosol valve is crimped onto the mounting cup with a diaphragm disposed between the top of the valve body and the mounting cup. This diaphragm seals around the valve stem, which is depressed downward for dispensing, along with sealing at the top of the valve body.
In general, two types of aerosol valves are in common use. There are a metering valve and a non-metering valve. The construction of the metering valve is such that a chamber is formed in the valve body. The chamber is of a size to hold a metered dose of the product to be dispensed. When the valve is in an unoperated position, the tank formed in the valve body is placed in communication with a dip tube extending to the bottom of the can and the tank is filled with the product to be dispensed under pressure. Upon the depression of the valve stem, the inlet from this dip tube and, thus from the container, is closed off and an outlet through the upper part of the stem is then opened. The material under pressure in the tank is forced out through the dispensing outlet. In a non-metering valve, on the other hand, the tank is always in communication with the dip tube and thus with the container. As a result, depressing the valve to place the outlet in communication with the tank provides for a continuous supply of material to be dispensed.
Generally, there are two methods of getting the propellant into the container. One type is cold filling in which the propellant is maintained in liquid condition by being cooled and is filled into the container in that manner. This, of course, requires special refrigeration equipment to maintain the container and the propellant at a low temperature until the mounting cup and the valve therein can be crimped in place on top of the container. Cold filling is not at all practical in some cases. For example, when using hydrocarbon propellants, which have become more common due to the problems caused by fluorocarbons, cold filling presents significant dangers. Because a certain amount of the propellant will escape during cold filling, a collection of hydrocarbon such as butane in the air can result and can cause an explosive danger.
The other method of filling is known as pressure filling. In this method of filling the propellant is forced into the container, generally through the dispensing outlet in the valve stem. The rate of dispensing from the valve is normally controlled by an orifice or outlet port in the stem. Generally, this orifice is small. This places a limit on the filling rate. A further problem exists, particularly in a metering valve, since when the valve is depressed, at which time it would be possible to force the material under pressure through the valve stem and into the tank, the tank is sealed off at the bottom. One solution to this problem has been to place a cross-cut in the stem which, if the valve is depressed further than it would be in normal operation, bridges the seal at the bottom of the tank to permit the material to flow from the tank and into the container. This solution although workable is still slow because of limitations on the size of the orifice and it requires a more complex construction of the valve stem.
Another solution is that disclosed in British Pat. No. 1,287,126. In this arrangement for pressure filling, openings are made at the top of the valve body at the edges. Normally these holes are covered by the sealing ring or diaphragm at the top of the valve body by means of which the valve is sealed to the mounting cup. In this method of pressure filling the material under pressure, after it reaches the tank, forces its way under the sealing ring and finds its way to the holes whereupon it reaches the container. Although this works reasonably well, there are still limitations on filling speed. In the valve disclosed in the British patent, the valve body is made of metal. Similar construction has been used with plastic. However, in each case the design is such that under normal conditions a seal is formed between the valve body and the mounting cup at the top of the valve body. Some sort of seal is necessary in order to prevent the material under pressure or the propellant from escaping. However, this method of pressure filling is still relatively slow.
Another manner of pressure filling is disclosed in U.S. Pat. No. 2,974,453. In this arrangement, a two piece stem is used. By using a two piece stem, interchangeable upper stem portions become possible. Thus, a stem with a port at its lower end is used for pressure filling, whereas a stem with a port further up is used for dispensing. This, of course, results in increased complexity of the aerosol valve.
In some applications, there is also a need for fast pressure filling in leak proof pump type dispensers such as the type of dispenser disclosed in U.S. Pat. No. 3,211,346. This need exists in the dispensing of products which cannot tolerate the presence of air, which could result in the oxidation of the product. Such is the case with certain sensitive drugs. Conventionally, pumps include means for venting so that, as material is dispensed and removed from the container, the space vacated is filled with air. In this way, ambient air pressure is always available acting on the remaining fluid within the container. However, with any venting system, there is some danger of leaking. Thus, where it is desired to make an absolutely leak proof pump, measures such as that disclosed in the aforementioned patent have been taken. Essentially this comprises making the pump and container airtight and pressurizing the container to a pressure above atmospheric, using nitrogen or the like, so that even when the material in the container reaches a low level, there will still be a pressure equal to or greater than atmospheric pressure to permit refilling the pump chamber.